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Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 20113. RESULTS AND DISCUSSIONIn tabel 1 there are presended the results concerning size distribution of cells incubated 24hours in the presence of nalidixic acid (inhibitor of DNA gyrase in Gram-negative bacteria)and yeast extract.Table 1. The average length of cells obtained from measurement of 150 cells by TEM andepifluorescence (EFM) technique; samples were taken at the beginning of the incubation period ( T 0 )and at 24 hours ( T 6 ).incubationtimeaverage length of cells - µm (TEM)M1 M2 M3 M4 M5T o 0.590 0.800 0.610 0.900 0.830T 6 , 24 h 1.400 2.250 1.150 4.750 2.900incubationtimeaverage length of cells - µm (EFM)M1 M2 M3 M4 M5T o0.729 1.012 0.803 1.121 1.105T 6 , 24 h 2.597 4.264 1.996 7.888 4.118One can see that there are some differences obtained with respect to cell length measuredby epifluorescence microscopy and by transmission electron microscopy. Figure 1 and 2are showing the correlation between the average length of cells at initial time (T 0 ) and finaltime (T 6 ) on direct assessment of the number of viable cells, obtained by TEM- negativestaining and epifluorescence technique/ software Image J.Figure 1. Correlation between TEM and EFM values of the average length cells at the time zero, inthe five microcosms. Continuous line represents the linear regression: y=1.269x + 0,006(r = 0.983; n = 5)142
Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011Figure 2. Correlation between TEM and EFM values of the average length cells at 24 hours ofincubation time in the presence of nalidixic acid, in the five microcosms. Continuous line representsthe linear regression: y=1.561x + 0,284 (r = 0.981; n = 5)The results show a good linear correlation between cell length measurements obtained byboth methods (TEM and EFM), with the specification that the size cells based on EFMmethod is generally higher than that obtained by TEM. This could be attributed to use ofdifferent magnification of the images in both methods, and different methods to prepare thebiological probes for either EFM or TEM (Chen et al., 2001). The dehydration step couldproduce a decrease in cell dimensions (Wang et al., 2000; Wrigley N.G., 2004).Our results showed a variation in time of the size of individual bacterial populations in thefive natural microcosms.These investigations allowed us to highlight the very small coccoid forms (diameter < 0.25µm) when they were viewed by epifluorescence; however, when inspected by TEM onecan see that some of the cells are actually rods and vibrio (Figure 3).Figure 3. Minibacteria: rods, cocci and vibrio (diameter < 0.25 µm)143
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